function y=X(x)
    %y=exp(-4.222)*x^0.7307;   % Manufacture
    y=exp(-4.443)*x^0.7643;    % Use
    %y=exp(-2.12)*x^0.4562;
    %y=exp(-4.2222)*x^0.7307;   % Manufacture
    %y=exp(-4.4435)*x^0.7643;    % Use
    %y=0.00728*x+0.4156;
end